Boiler Chemical Cleaning
After a boiler is constructed, or after a certain number of years of operation, it is common that a boiler needs a chemical cleaning. This is needed to remove grease, loose debris/metal, dirt and corrosion in the case of just built boilers. Boilers that have been in operation for a long time, and especially those where water chemistry is less that ideal, can develop scale which also needs a chemical cleaning to be removed.
If a just built boiler is not cleaned, then debris can be blown into the turbine and cause damage to the baldes or control valves. Grease would decompose into organic acids that would cause corrosion. Two kinds of chemical cleanings can be done in this case: a caustic boil out and steam blow out or an inhibited acid clean with a surfactant clean step to remove grease.
Acids that are commonly used in boiler chemical cleaning are hydrochloric acid, hydrofluoric acid, citric acid and phosphoric acid. A corrosion inhibitor is usually added to prevent the acid from attacking the bare metal once the oxides and scale are removed. Sometimes Chelants like EDTA are used to help remove scale. Also passivating agents lke hydrazine can also be used to passivate the metallic surface after an acid clean.
Specialist companies that do boiler chemical cleaning are:
Here is an interesting paper on boiler chemical cleaning from the EPRI.
Compiled by Rami E. Kremesti M.Sc.